In a time division multiple access (TDMA) satellite communication system, the various ground stations are assigned separate time slots within a frame period for transmitting bursts of information to other ground stations and for receiving bursts of information from other ground stations. In order to transmit or receive bursts of information within the proper assigned time slot of a frame interval, various synchronization and acquisition techniques have been proposed.
For example, in U.S. Pat. No. 3,643,031, issued to H. Sasaki et al on Feb. 15, 1972, a burst synchronization control unit is disclosed wherein counters count the frame periods to forecast the reception in the next frame period and a unique word detecting circuit then provides station discrimination from control information included in each received burst.
U.S. Pat. No. 3,730,998, issued to W. G. Schmidt et al on May 1, 1973, discloses a TDMA satellite communication system which generates aperture windows for acquisition purposes. For the receive side thereof, the TDMA signal is received and a demodulator recovers a clock signal and two data streams which are applied to a differential decoder unit and, in turn, to both a preamble detector and a descrambler unit. The preamble detector and an associated aperture generator function to detect frame markers which are used to synchronize bursts. The descrambler unit descrambles a unique word in each burst and applies such word to a demultiplexer unit which operates to extract signals in designated bursts and sub-bursts and apply such signals to a control unit or a proper terrestrial interface module.
With the proposed use of higher and higher data rates in satellite communication systems, the problem remaining in the prior art is to provide a processor for a TDMA burst modem with simple high-speed hardware while providing improved synchronization accuracy and reliability of modem operation with short length unique words.